The present invention relates to a conveyor apparatus for a pourable material to be conveyed, for example a synthetic resin (i.e., plastic) granulate or powder, with a plurality of handling devices for processing the material to be conveyed, a storage bin for the material to be conveyed as well as a conveying line provided with a suction probe or wand for sucking in the material to be conveyed and a low pressure source connected to the conveying devices via a suction line.
To produce synthetic resin articles that are made, for example, of thermoplastic polyester, such as polyethylene terephthalate (PETP), using an injection molding machine, a dry synthetic resin granulate is fed to this machine. Because the synthetic resin granulate often contains moisture when delivered, this moisture must be removed from the granulate before it is supplied to the processing machine. To remove the moisture, substantially cylindrical dryers are used into which the moist granulate is filled. A hot, dry airstream passed through the granulate in the dryer removes the moisture from the granulate. After a sufficient residence time of the granulate in the hot, dry airstream, the dry granulate can be removed from the dryer and supplied to the processing machine. Such a system is disclosed, for example, in Karls, U.S. Pat. No. 5,182,871 (=EP 487,829).
In relatively large production plants with a plurality of processing machines, these machines are supplied with dry granulate by a plurality of dryers which are charged with moist granulate as needed from a central storage bin. Used for this purpose are conveying lines to which the individual dryers, also referred to as conveying devices, are connected. Each conveying line is provided with a suction probe, which dips into the storage bin to remove granulate. The granulate is sucked out of the storage bin by means of negative pressure. For this purpose each of the conveying devices is connected to the suction end of a pump via a common suction line.
In the described plants, the individual dryers are often spaced far apart from one another, e.g., at a distance of 100 meters. If each dryer is connected to its own conveying line, the diameters of the conveying line and the suction line are determined not only in view of minimizing granule abrasion, dust development and pipeline wear but also as a function of the location of the respective dryer relative to the storage bin. The development of dryer-specific conveying lines and suction lines, however, is costly and time consuming.